This document introduces ScalikeJDBC, a type-safe SQL library for Scala that provides a non-blocking approach to database access. It summarizes ScalikeJDBC's features, including its DSL for writing queries, SQL interpolation support, and an asynchronous version called ScalikeJDBC-Async. It also briefly introduces a new Scala web framework called Skinny that is inspired by Ruby on Rails and uses ScalikeJDBC.

1. JDBC-like non-blocking
DB Access in Scala
@seratch
Kazuhiro Sera Kabukiza.tech
is a workshop
which is presented
by Dwango
at Kabukiza tower

2. ScalikeJDBC
- DB Access library in Scala
- “Never stuck when using at work“
- SQL, flexibility, expandability,
speedy bug fixes and releases
- Cool enough though it’s less well-
known than Slick or Squeryl.

3. DSL Example
import scalikejdbc._, SQLInterpolation._
val memberId = 123
val member = DB readOnly { implicit session =>
withSQL {
select.from(Member as m)
.where.eq(m.id, memberId).and.isNull(m.deletedAt)
}.map(Member(m)).single.apply()
}

4. SQL Interpolation
import scalikejdbc._, SQLInterpolation._
val memberId = 123
val member = DB readOnly { implicit session =>
sql”””select id, name from member
where id = ${memberId} and deleted_at is null”””
.map(Member(m)).single.apply()
}

5. Get things done
- Easy to understand, few pitfalls
- No need to google framework
specific knowledges
- Easy to find the first developer who
use it correctly (required background
is only Scala basics and SQL)

6. Productive
- Mostly type-safe DSL
- Source code generator from
existing tables via sbt plugin
- Logging slow queries, it’s also
possible to send data to external
services (e.g. Fluentd)
- AutoRollback testing support for
specs2、ScalaTest

7. ScalikeJDBC-Async
- ScalikeJDBC compatible API, but it
doesn’t use JDBC internally
- Inspired by Activate ‘s async API
support (2013/7)
- Though some introduction
examples are already reported, this
library is still in the alpha stage.

8. How?
- Just wrapped postgresql-async/
mysql-async by @mauricio
- Netty based database driver which
is not compatible with JDBC
- ConnectionPool with queue
- Transaction = begin/commit in a
non-shared connection

9. Mostly same!
import scalikejdbc._, SQLInterpolation._, async._
val memberId = 123
val member = AsyncDB withPool { implicit session =>
withSQL {
select.from(Member as m)
.where.eq(m.id, memberId).and.isNull(m.deletedAt)
}.map(Member(m)).single.future()
}

10. Transactions with for
comprehensions
val name = “Typesafe”
val programmers = Seq(“Alice”, “Bob”, “Chris”)
val resultFuture = AsyncDB localTx { implicit tx =>
for {
company <- Company.create(name)
employees <- company.hireAll(programmers)
} yield ()
}

11. Tips
- Since you need to work with many
Future[Option[_]] and Future[List[_]],
for comprehensions are suitable
- Play2’s Action can receive Future
values, pretty good chemistry

12. One more thing
This is a Lightning talk,
but I have “One more thing”.

13. Really Must?
Indeed, some kinds of
applications need non-
blocking DB access.
However, many smaller
applications actually exist.

14. Most cases?
- “Our application is built with Servlet
& JDBC. No problem.”
- “C10K? It’s not my problem.”
- “Just need simple admin CRUD app.”
- “Good at Java, but Java in 2013??”

15. Rails?
Reasonable choice for front end apps.
I myself am working with API servers in
Java and Rails front end at the office.
Oops, most of you here would like to write
Scala apps, right?

16. Grails?
If you’re not a Groovy lover...
Oops, most of you here prefer Scala than
Groovy, right?

17. Play2?
I understand Play2 makes Reactive/real-
time app development productive.
Indeed, looks like Rails app but Play2 is
neither new Rails nor new Play1.

18. Skinny!
Small & full-stack web app framework in
Scala is still absent. So I just started
developing Scala on Rails which is
named “Skinny Framework”!
Built with Scalatra + ScalikeJDBC + more,
API is highly inspired by Rails.
http://git.io/skinny

19. ORM Example
case class Developer(id: Long, groupId: Opion[Long],
group: Option[Group] = None, skills: Seq[Skill] = Nil)
object Developer extends SkinnyCRUDMapper[Developer] {
belongsTo[Group](Group, (d, g) => d.copy(group = g)).byDefault
hasManyThrough[Skill](DeveloperSkill, Skill, (d, skills) => d.coply(skills = skills))
def extract ...
}
Developer.findAll()
Developer.findById(123)
Developer.createWithAttributes(params.permit(“id”, “groupId”))
Developer.updateById(123).withAttributes(attrs)
Developer.deleteById(123)

20. Thanks
- There is no async JDBC
- ScalikeJDBC introduction
- ScalikeJDBC-Async introduction
- Skinny Framework introduction